Originally Posted by http://www.sheldonbrown.com/brandt/machined-rims.html
Even anodizing, which is a hard ceramic, whether thick or thin, is more durable than the machined rim. However, anodizing is not the solution to wear, because it degrades braking. Anodizing being an insulator that overheats brake pads and causes brake fade.
why wouldn't you get the machined front if you know you're going to use a brake (and the brake will machine an unmachined wheel if you don't)?